On gun control via government purchasing

As I do on occasion, I was perusing some of the various gun control groups sites and seeing what they were up to. In so doing, I discovered an interesting proposal that I had not previously known about: using the purchasing power of government agencies like police departments to implement gun control.
Although some people, including former Governor of New York Elliot Spitzer, have written about such strategies in the past, I’ve not heard of it before now. Gov. Spitzer’s explains the strategy:

Here is how it could work with guns: The Defense Department and the city of New York are among the largest purchasers of guns. If the president and the mayor truly believe that semi-automatic weapons should not be available to private purchasers, and that magazines with more than 10 bullets should not be sold over the counter, they should simply say that, from now on, the federal government and the city of New York, as a matter of public safety, will not buy any weapons or ammunition from companies that do not agree to pull semi-automatics from their stock and refuse to produce magazines with more than 10 rounds other than for sale to the government. President Obama and Mayor Bloomberg should announce that semiautomatic handguns with high-capacity magazines?the kind used in Oak Creek; Aurora, Colo.; Tucson, Ariz.; and Virginia Tech?can no longer be sold to private citizens by any company that wants to do business with the federal government and the city of New York.

The major gun manufacturers will agree to the limits imposed by their major customers.

Gov. Spitzer’s plan is certainly interesting, but it relies on a few key assumptions without which the entire scheme collapses:

Government sales constitute a sufficiently large fraction of gun sales that manufacturers would be unwilling to lose their business, thus restricting what’s available for public sale to keep government business.

No other manufacturer would step in to fill the gap left by those playing along with the government.

While point #1 may apply to certain companies that are particularly reliant on government sales (what’s the breakdown of government:civilian sales for companies like, say, Colt?), it’s unlikely to matter for a lot of the smaller companies — I doubt that Stag Arms, Mega Arms, Magpul, and other relatively small manufacturers of somewhat “controversial” things like AR-15s, magazines holding more than 10 rounds, or guns with black plastic bits really care much if the Defense Department or the government of the State of New York don’t buy their stuff because they probably don’t buy their products already. They can’t lose sales they’re not already making, so this strategy can’t apply any sort of leverage against them.
Point #1 also breaks down when you look at sales figures: sure, a government agency may be the largest single customer of a particular company, but they make up a relatively small amount of total sales. As an example, let’s be generous and say that the State of New York is a manufacturer’s largest single customer and contributes to 10% of the company’s total income with the rest coming from smaller customers (e.g. local police departments, say a combined total of 10%) and individual buyers (80%). Even if the local police departments play along with the state, why would a company eschew 80% of its sales to appease a minority of its customers? That wouldn’t be good publicity for the company, particularly when the government makes it clear that they’re doing this specifically to apply leverage — what’s to stop the government from asking for more in the future and cutting off purchases if they don’t get what they want?
Point #2 reflects the state of the market: ARs are among the most popular guns in the country for private citizens. Manufacturers have been running around-the-clock to keep up with demand and there’s still a backlog. It would be foolish in the extreme for one company to simply give up their share of that market, generate enormous customer backlash, and allow other companies to take their place. There’s plenty of competition in the market, and while there might be some disruption if one of the big contract forges/casting houses leaves the market, someone else will happily take their place. Again, while the government might be the largest single customer of certain companies, they almost certainly make up a relatively small fraction of their over all sales, and there’s plenty of companies who don’t really care about government sales and so wouldn’t be pressured at all.
This doesn’t even begin to take into account that there’s a huge number of guns that are hugely popular with private citizens but almost never purchased by government buyers — how many governments purchase imported AK clones? Saiga shotguns? Ruger Mini-14s (yes, I know they’re reasonably popular with officers in jails/prisons, but you rarely see police using them outside of that context)? How many agencies buy Kel-Tec rifles, Kahr pistols, M1As, or any of the zillions of other products that anti-gun people would restrict if they could?
Of course, the strategy doesn’t take into account the fact that the government is a purchaser of items, not a manufacturer. If the large manufacturers decided to stop selling their products to the government (Barrett was the first major company I can recall that did this, and now there’s quite a few other companies who refuse to sell guns or accessories to governments in states that infringe the rights of private citizens). I think it’s more plausible that gun companies would band together and refuse to sell or service products to governments that infringe the rights of their citizens (thus applying leverage to change policy for the better) than for governments to use their relatively minor purchasing power to influence gun companies.
As always, I welcome the thoughts and comments of readers.